1. Field of the Invention
The invention relates to the surveillance of an aircraft's environment. In this instance, by surveillance, we mean the aircrew's knowledge and management of information about the environment in which the plane travels, such as weather conditions, terrain and traffic.
2. Discussion of Prior Art
In general, each type of information is provided by a dedicated surveillance set (radar, warning system, etc.). The information gathered is forwarded to the aircrew via a display and/or an audio system.
On some planes, these surveillance systems are advantageously part of one single surveillance system of an aircraft's environment, commonly called “Aircraft Environment Surveillance System” (AESS).
In order to make sure the system is available and reliable, each surveillance set is at least duplicated. Therefore, an AESS groups together at least two electronic systems, called “Aircraft Environment Surveillance Units” (AESU), where each one groups together several redundant surveillance sets.
In order to simplify things, a master/slave type of architecture is chosen to manage the transfer of information to the reproduction devices (display, audio system, etc.). Thus, in normal mode, only information obtained from the master surveillance system sets are sent to the aircrew.
If a master surveillance system set is not available, an “Electronic Centralized Aircraft Monitoring” (ECAM) procedure asks the pilots to use a command panel, provided for this purpose, to reconfigure the systems, and thus give the status of master system to the previously slave system in order to extract all the information.
However, this process has disadvantages, namely, in case of a crossover failure of two sets. In this instance, by crossover failure we mean the simultaneous unavailability of a surveillance set of a first system and a non redundant surveillance set (that does not have the same type of information) of a second system.
Indeed, in this situation, the aircrew must choose between the data of the first system and that of the second system. For example, if the terrain surveillance set of the first system and the weather conditions surveillance set of the second system are both faulty, the team must choose between the terrain data and the weather warnings.
Although, in most cases this choice is easy, some situations, such as an approach or a take-off in bad weather in mountainous terrain, make things more difficult.